1. Field of the Invention
A new Ziegler type catalyst system for alpha olefin type polymerization includes at least one supported Group IVB-VIII transition metal halide, a highly hindered amide having the formula R'.sub.2 YNR.sub.2 and at least one Lewis base, wherein R' is selected from the group consisting of C.sub.1 to C.sub.20 primary alkyl, secondary alkyl, tertiary alkyl, neopentyl alkyl, branched alkyl, naphthenic, or aralkyl groups, R is selected from the group consisting of aryl groups, substituted aryl groups, C.sub.3 to C.sub.20 bulky alkyl, cycloalkyl, aralkyl, aryl or substituted aryl groups or R.sub.2 N is a cyclic amide group and Y is selected from the group consisting of aluminum, gallium or indium. The catalyst system provides high polymerization activity and increased crystallinity of the polymer.
2. Description of the Prior Art
There is extensive art on the polymerization of ethylene and higher alpha-olefins, including dienes, using Ziegler-type catalysts containing either alkyl metals or alkyl metals in which an alkyl group has been replaced by X, OR, SR, NR.sub.2, etc., in combination with a transition metal compound of Groups IVB-VIII, where X=halide and R=C.sub.1 to C.sub.20 hydrocarbyl substituent.
For commercial stereospecific polymerization of propylene and higher alpha olefins, only a few alkyl metal compounds have been found effective in combination with titanium or vanadium chlorides. Commercially, only R.sub.2 AlCl or R.sub.3 Al are used together with a crystalline form of TiCl.sub.3 or TiCl.sub.3 .cndot.nAlCl.sub.3. Mixtures of R.sub.3 Al and R.sub.2 AlCl and RAlCl.sub.2 are made in situ and have been disclosed as catalyst components frequently in the art. R is preferably ethyl (Et) or isobutyl; n=0.1 to 0.75.
It is also well-known that, in propylene polymerizations using TiCl.sub.3, catalyst activity decreases sharply in the series AlEt.sub.3, Et.sub.2 AlCl, EtAlCl.sub.2 (Malatesta, Can. J. Chem. 37, 1176 (1959) and Boldyreva et al, Vysokomolekul. Soedin 1, 900 (1959); C.A. 55, 2454a (1961). When the chloride in Et.sub.2 AlCl is replaced by OR, SR, SeR or NR.sub.2, activity and polymer isotacticity usually drop drastically (Danusso, J. Polymer Sci. C4, 1497 (1964)).
In one of the present inventor's research, Et.sub.2 AlOEt and Et.sub.2 AlNEt.sub.2 were found to have some activity with TiCl.sub.3, but the polypropylene obtained was nearly atactic (Langer, Seventh Biennial Polymer Symposium, Florida, Dec. 8, 1974). Therefore, the art teaches that both activity and polymer isotacticity are extremely low when R.sub.2 AlNR.sub.2 (aluminum amide) compounds are used as replacements for conventional alkyl metal cocatalyst components.
U.S. Pat. No. 3,418,304 discloses a complex of alkyl metal compounds such as Et.sub.2 AlNEt.sub.2 and Lewis acid salts such as AlCl.sub.3 and MgCl.sub.2, e.g., Et.sub.2 AlNEt.sub.2 .cndot.AlCl.sub.3 as cocatalysts to entirely replace conventional aluminum alkyls, but such complexes are entirely different from the concept of utilizing certain hindered aryl amides and Lewis bases as cocatalysts for supported TiCl.sub.3 or TiCl.sub.4.
U.S. Pat. No. 3,255,169 discloses a Ziegler catalyst system employing aluminum hydroaminate compounds. Typical of these is HAl(NHC.sub.2 H.sub.5).sub.2 which is unrelated to the dialkyl aluminum hindered amides of this invention.
Recently, U.S. Pat. No. 3,905,913 has issued disclosing the use of ##STR1## where X is H or halogen, both Rs are hydrocarbon radicals; and R' is a divalent hydrocarbon radical. These compounds are not closely related to those of the invention herein, and they would be inactive in this invention.